PSI - Issue 77

Georg Veile et al. / Procedia Structural Integrity 77 (2026) 348–356

349

2

Georg Veile et al./ Structural Integrity Procedia 00 (2026) 000–000

Keywords: Fatigue; Gradients; Weld topology; FEA; Simulation; Scan;

Nomenclature calc

calculated/predicted

BM

Base metal

delta

d

experimental

exp FDP FEA FGF FFS

Fatigue Damage Parameter(s) Finite Element Analysis

Fesich-Gupta-Fesich Fesich-Fatemi-Socie

FS

Fatemi-Socie

Material parameter

k

maximum

max

Mdn. Median n normal N

Number of cycles NURBS Non-Uniform Rational B-Splines RM Rettenmeier Sd. Standard-Deviation SWT Smith-Watson-Topper WM Weld metal x,y,z

Direction of vectors in the coordinate system

ε σ γ τ χ Δ

strain in (mm/mm) stress in (MPa) torsion in (MPa) gradient (1/mm) shear strain in (mm/mm)

delta

1. Introduction Local approaches hold potential to reduce conservatism in fatigue life assessment. Here, weld joints can be modeled with fictitious radii, e.g. 1 mm [1,2]. Thereby, non-local approaches are already outperformed with regard to accuracy [1]. Further improvement may be realized with the implementation of realistic weld joint topologies. However, this comes with an increase of time for modeling and simulation. Nevertheless, in [3] it was shown that fatigue life assessment of scanned weld joint topologies with different fatigue damage parameters (FDP) shows an increase in scatter compared to fatigue life prediction with idealized weld radii (see Fig. 1). When compared to the idealized weld radii, scatter reduction could only be achieved with retrospective changes in initial parameters, such as the material model, by means of least square error [4,5]. The retrospective change is however no applicable method for fatigue life assessment [3]. In references [3,5], sufficient prediction was achieved with gradient based FDP. The influence of gradient determination is significant, as studied by Louks et al. [6], Braun et al. [7] or Spaggiari et al. [9] with the theory of critical distance classical evaluation of stress gradients.